With the advancement in scientific technologies and the modularization and miniaturization of camera lens, it is now possible to produce digital cameras having a very small volume, and most of currently available mobile phones are provided with the function of a digital camera. In a miniature lens, there are many different auto-focusing driving mechanisms. Among others, voice coil motor (VCM) is the currently most widely adopted auto-focusing driving mechanism. The VCM has the advantages of small volume, low power consumption, accurately actuated displacement, and cost-effective, and is therefore very suitable for short-distance driving in miniature lens auto-focusing.
FIG. 1 is an exploded perspective view showing that a conventional movable lens focusing mechanism includes an upper cover 10, a lower cover 11, a lens holder 12, and a an outer frame 13 being provided at four inner wall surfaces with a magnet 14 each. The lens holder 12 is internally provided with screw threads 15 for a lens 16 to screw thereinto. A winding 17 is wound around the lens holder 12. The lens holder 12 is supported by an upper plate spring 18 and a lower plate spring 19 to be axially movably located at a center in the outer frame 13 and surrounded by the four magnets 14. When the winding 17 is supplied with an amount of electric current to thereby produce a magnetic field polarity, the lens holder 12 and the four magnets 14 mutually repulse or attract, bringing the lens holder 12 and accordingly, the lens 16 to displace for focusing.
When the lens 16 is being screwed into the lens holder 12, a torsion force is produced and applied to the lens holder 12. Since the upper and the lower plate spring 18, 19 connected to and supporting the lens holder 12 have a relatively small thickness, which is generally as small as 0.06 cm, and include relatively thin elastic bendable portions, as shown in FIG. 2, the two plate springs 18, 19 tend to deform or even break due to the torsion force produced at the time the lens 16 is screwed into the lens holder 12.
To enable a movable lens focusing mechanism with low power consumption and quick displacement, the elastic members for supporting the lens holder 12 have been designed to be elastically movable in an axial direction without any elastic protection in lateral directions. Under this condition, a lens just could not afford to fall because a big impact due to falling would cause the lens to displace laterally and result in damage of the elastic members. That is, the lens would become damaged or useless due to lack of elastic protection in the lateral directions.
It is therefore tried by the inventor to develop a structure for protecting the elastic members in the miniature lens against deformation.